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Calculating friction

  1. Jan 13, 2012 #1
    1. The problem statement, all variables and given/known data

    A sled weighing 70kg, going at 14 m/s, slides down a ramp 3 m high. It's final velocity is 15.6 m/s. How much energy was lost due to friction?


    2. Relevant equations

    .5mvi2 + mgh = .5mvf2 + x

    where x = joules of energy for friction

    3. The attempt at a solution

    step 1 .5(70)(142+70(9.8)(3) = .5(70)(15.62 + x

    step 2 6860 + 2058 = 8570 + x

    step 3 6860 + 2058 - 8570 = x

    step 4 401 = x

    The books says the answer is 74
     
  2. jcsd
  3. Jan 13, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I'd say that you were correct. (8570 is a typo, though.)
     
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